The Lateral Nasal Glands of Amphiuma. 157 



size (perhaps generally one in each set) become annexed to the main 

 gland. In this process of annexation we have an explanation of the 

 somewhat isolated anterior lobe of the adult gland already alluded 

 to (Plate I, Fig. D, alb), a lobe which probably arises separately 

 and only secondarily becomes connected with the main gland. The 

 atrophy of another accessory duct explains, also, the existence in 

 this case of an additional short duct (ad) ending blindly with no con- 

 nection with the ghmdular mass. 



This atrophy of ducts of accessory tubules and their secondary con- 

 nection with the main gland indicates a physiological demand for 

 concentration of the secretion at a single point; on the other hand, 

 there should be mentioned, as a possible cause for this atrophy, the 

 fact that a Trematode parasite (as yet unidentified) is frequently 

 found lodged in close proximity to, or even within, the lucts of the 

 glands. This parasite is not confined to this region, for it has been 

 found lodged in the muscles of various parts of the head, and in the 

 connective tissue underlying the skin and the epithelium of the 

 mouth and nasal cavities. So far as I know, the structure and life- 

 history of this Trematode have not been worked out. It is possible, 

 however, that the ducts of the lateral gland are vulnerable points 

 through which the parasite frequently gains entrance; the presence 

 of such a parasite within or near one of the ducts would be very 

 likely to cause its atrophy, while the glandular region of the tubule 

 would establish a secondary communication with the exterior through 

 a neighboring branch of another tubule and would thus continue its 

 functional activity. 



III. The Homology of the Lateeal Nasal Gland and Its 



ASS0CLA.TED STRUCTURES. 



In both the Salamandrida and the Anura there are certain tubular 

 glands which open in close association with the external naris and 

 are known as the external nasal glands. The number of these glandu- 

 lar tubules associated with each naris varies in different species from 

 two to fifteen. These structures have long been recognized and their 

 relationships have been worked out in various species by Wiedersheim 

 '76, Seydel- '95, Kiese '91, Born '76, and Bruner '96 and '01. 



